Many drinking water treatment plants are currently using alternative disinfectants to treat drinking water, with ozone, chlorine dioxide, and chloramine being the most popular. However, compared to chlorine, which has been much more widely studied, there is little information about the disinfection by-products (DBPs) that these alternative disinfectants produce. Thus, it is not known if the DBPs from alternative disinfectants are safer or more hazardous than those formed by chlorine. To answer this question, we have set out to comprehensively identify DBPs formed by these alternative disinfectants, as well as by chlorine. The results presented here represent a compilation of the last 8 years of our research in identifying new DBPs from ozone, chlorine dioxide, chloramine, and chlorine. We also include results from recent studies of Israel drinking water disinfected with both chlorine dioxide and chloramine. Over 200 DBPs were identified, many of which have never been reported. In comparing by-products formed by the different disinfectants, ozone, chlorine dioxide, and chloramine formed fewer halogenated DBPs than chlorine.